Sequential Float Charge Controller (Formerly: Long Delays with the 555 Timer)

Discussion in 'Digital Circuit Design' started by iONic, Jan 19, 2019.

  1. Alec_t

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    One thing to watch with a differentiator like that is that the input protection circuit of a CMOS IC, such as the 4017, is not overloaded when the pulse voltage goes beyond either supply rail.
     
  2. crutschow

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    I think we've established that he doesn't need a differentiator.
     
  3. KeepItSimpleStupid

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  4. iONic

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    After delving into the ICM7242 Timer datasheet I realize the following:

    IC.JPG


    waveforms.JPG

    No problem getting the 10min, 20min, 40min, but I will need 2 additional IC's @ $270/ea. for which I have only one. Either that or I would need to switch between 3 separate RC networks. The timing part of the circuit would look like this:

    ICM7242.JPG
    I also believe I'd need to invert the signals from the ICM7242 to match the 4017.
     
    Last edited: Jan 20, 2019
  5. ElectricSpidey

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    If you need to invert a clock signal to a 4017, just tie the clock high and clock the CE instead.
     
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  6. iONic

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    I'm now eyeing the 4521 vs 4060 as I do not have 3 ICM7242's and they are $2.70/ea. I have both the 4521 and the 4060. I'm kinda leaning towards the 4521 Freq. Divider. Anyone know what value for Rs?


    upload_2019-1-20_16-48-28.png

    Oddly I see two different configurations for the chip regarding the Rs, Rtc & C.
    There are two different datasheets for two different mfgr (MC14521 & CD4521).
    The pinout is identical.
     
    Last edited: Jan 20, 2019
  7. ian field

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    Limiting factors are mostly leakage in large timing capacitors and high value resistors tend to "wander off" - I'd go for a 555 running at a more practical frequency and get longer periods by squirting the pulses through a CMOS ripple counter.
     
  8. djsfantasi

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    As several people have suggested
     
  9. danadak

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    I will be happy to help.

    Regards, Dana.
     
  10. iONic

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  11. iONic

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    eetech00,
    Been admiring your take on the "Sequential Battery Float Charger." I appreciate you taking the time to come up with a solution. Surprisingly, I have all the chips(I believe): (2) CD4017, (1)CD4060, (1)Hex Inverter, and (1)AND Gate.
    I like the solution for selecting the three different time periods, albeit requiring 2-3 additional chips.

    The two 6.8uF Caps used for the initial timing (connected back-to-back), is this read as a 3.4uF/non-polarized cap?

    My source voltage for the circuit will be two CR123 rechargeable batteries in series(6.0V) as I would expect them to last a fair amount of time(4 months continuous operation). I may be all wet with that guess, and if so I would resort to a spare cell phone charger@ 5V.

    I had been pondering the Indicator LED's attached to the MOSFETs. Placing them on the drain will work just as well.
    I would also have to add Indicator LED's for the three time periods. I should be able to tap off of the 4017 Selector IC, Q0, Q1, Q2, yes.

    Building this iteration of the circuit is not set in stone, though, as I am in talks with eetech00 with respect to creating a uP for the job. Been wanting to get involved in this for some time. We'll see how our arrangement turns out.
     
  12. eetech00

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    Jun 8, 2013
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    Yes...The 4060 RC timing circuit requires a non-polar cap.

    You can tap off the 4017 but there's only about 4ma available from each output. You can add driver transistors if necessary, or use low power LEDs instead.

    o_Oumm....I think you meant dendak :D

    Good luck,,

    eT
     
  13. crutschow

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    Below is the LTspice simulation of a CD4040 12-bit counter (I don't have a model for the CD4060) driving a CD4017 .
    With a 1.17s clock period, the Q9 (divide by 512) output has a 600s period (10 minutes).
    You can see this sequentially advancing the CD4017 output every 10 minutes.

    Note that you only require one timing chip as the Q10 output will have a 20 minute period and Q11 will have a 40 minute period.

    upload_2019-1-20_23-31-35.png
     
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  14. iONic

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    Setup the first stage of the circuit by eetech00. Despite trying three different make of the 4017 decade counter (CD4017B, HCF4017B, & M74HC4017B) and could not get one to work. Tried multiple chips of each make, kept the diode, removed the diode, kept the cap, removed the cap, tried both 5V & 12V, moved the chip on the breadboard, Rewired...etc.

    CD4017.JPG
     
  15. crutschow

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    I see several problems:

    Each LED need a resistor in series.

    The clock has nothing to pull the signal to ground (it won't go there by itself). Add a 10kΩ resistor from the clock input to ground. A floating CMOS will float to an undefined state.
    An open circuit CMOS input is not logic zero.
    Never-ever let a CMOS input float. :eek:

    If PB is a mechanical switch the contacts will bounce when energized, generating multiple clock pulses with each closing. You need to add a debounce circuit (Google it).

    D1 serves no purpose and allows the Reset input to float to an undefined logic state. Remove it and connect output 3 directly to RESET.
     
    Last edited: Jan 21, 2019
  16. danadak

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    You are trying to clock the clock with a mechanical push button. Thats
    not good as they bounce due to inertia generating many clocks on a single
    press.

    [​IMG]


    You have to debounce the button. Many ways to do this, also using code in
    UP.

    [​IMG]

    Regards, Dana.
     
  17. iONic

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    Thanks crutschow & danadak!
    The diode will likely be necessary later when I connect additional circuitry. I had tried it with and without. The LED's do need resistors, but given the 5V supply and testing, I omitted them as they would be momentary. The switch debounce circuitry was used initially and didn't "seem" to make a difference so I began leaving it out. But this would be the likely culprit.
    Will add the debounce circuitry tomorrow AM and report back.
     
  18. Alec_t

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    Being momentary is not important for survival of the LEDs or the IC, but even momentary excessive loading of the CMOS outputs could affect the operation of the IC.
     
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  19. iONic

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    So much for a "morning" reply.
    Built the circuit below. Upon power-up, Pin 3(4017) lights up. Pressing the PB turns Pin 2 high, and with an additional press Pin 4 goes high. As one LED turns on, the other two LED's are off. However, this is consistent only when I press deliberately. If I press lightly or quickly the LED sequencing order can fail.

    Note: R1 & R4 are 8.2k, not 8.2 Ohms
    0-DebounceC.JPG

    I have read that all inverters are not created equal for TTL circuits. These are the Inverters I have on hand:

    - HCF4069UBEY(Hex Inverter)
    - MC14584BCP(Hex Schmitt Trigger)
    - MC74HC04(Hex Inverter High-Performance Silicon-Gate CMOS)
    - CD4050BCN(Hex Non-Inverting Buffer)
    - CD4010(Hex Buffers (Non-Inverting)


    Further observations:
    While waiting for replies, I did some more reading. I noticed that the 1uF capacitor I was using was polarized. I think it was a Tantalum cap. I switched it out for a .33uF ceramic cap and I could not replicate the bouncing effects. But!... I also tried the switch with no cap in the circuit and also had no fails. Then I reinserted the polarized cap and could not reproduce the fails either! Perplexed. Not sure if my values for resistors & cap are in the right ballpark, so insight on this would be helpful. From readings, I learned that the diode in the debouncing circuit helps speed up the switching. Also, the inverter should be taking care or the RC ramping characteristics.

    Q: Any advantage to debouncing from low side rather than high side? I can't see any, other than what may be simpler for the system/circuit.

    ALSO:
    - MM74HC14N(Hex Inverting Schmitt Trigger) Now in circuit

    Thanks peeps(people)...send me some more knowledge! Must have knowledge!:D
     
    Last edited: Jan 22, 2019
  20. crutschow

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    None of those circuits are TTL (bipolar), they are CMOS.

    Use the Schmitt trigger for U2.
     
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